The present invention concerns a fuel lock as part of venting arrangement for fuel tanks, and, more particularly, to a fuel lock having a casing to which are connected both an inlet conduit connected to the inside of the tank and an outlet conduit connected to atmosphere. The inlet conduit emerges into a volume of a casing space with a mouthpiece within the space located on an axial extent of the casing space which is above the maximum fuel level in the installation attitude and also when the fuel tank is on its side.
A fuel lock is shown in DE-PS 37 19 834 and forms a vessel which is interposed between two conduit sections constituting an inlet conduit and an outlet conduit of a surge conduit led away from a surge tank to the atmosphere. The inlet and outlet conduits are located, radially offset relative to one another in a common horizontal plane and each ends in the region of one of the end walls of the vessel. This configuration is arranged such that when the tank is on its side because of an accident, the vessel is above the fuel level. Fuel running out of the outlet conduit then sucks gas from the vessel. The quantity of gas present in the vessel is dimensioned so that it is sufficient to interrupt a syphon action on the fuel produced within the vessel. This satisfies safety conditions specified by the legislative authorities with respect to the outflow of a certain quantity of fuel during a limited period of time.
In practice, however, it has been found that in the case of certain extreme (and extremely rare) driving maneuvers, so much fuel can be forced from the fuel tank into the vessel by virtue of centrifugal force via the inlet conduit, with simultaneous compression of the gas in the vessel, that in the case where, because of an accident, the vehicle is on its side immediately afterwards so that the outlet of the outlet conduit comes to rest under the fuel level, both mouthpieces from the inlet conduit and the outlet conduit within the casing are located in the fuel. Therefore, fuel can be drawn into the vessel when fuel flows out of the outlet conduit and the fuel tank can run out.
An object of the invention is to improve a fuel lock so that, even in the case of an extreme situation described above or during a simulation of possible situations where the fuel tank is on its side or upside down, a continuous outflow of fuel is prevented or, alternatively, only the quantity of fuel tolerated by legislative authorities can run out freely.
This object has been achieved according to the present invention by subdividing the casing space into an inlet chamber and an outlet chamber which are connected together by a connecting conduit. The distance between the inlet conduit mouthpiece opening within the chamber and a partition separating the two chambers from one another is smaller than the distance between the partition and the connecting conduit mouthpiece opening in the inlet chamber. The connecting conduit emerges axially in the inlet chamber which, starting from the inlet side of the partition, is smaller than the chamber axial extent corresponding to half its volume. The outlet conduit enters the outlet chamber in the region of its end wall opposite the partition. The distance of the outlet chamber end mouthpiece of the connecting conduits viewed from the partition, in the axial direction is larger than the axial extent of the outlet chamber corresponding to half it volume. The outlet end mouthpiece of the connecting conduit and the outlet conduit mouthpiece within the chamber are spaced apart by a distance in the axial direction.
The casing of the fuel lock according to the present invention, which in the installation attitude of the fuel tank is located above the maximum fuel level, has an inlet chamber and an outlet chamber into each of which two conduits laying in a common horizontal plane emerge. One of these conduits forms a connecting conduit connecting the two chambers with one another.
The inlet conduit, connecting conduit and outlet conduit mouthpieces within the chamber form two break points in series in a vent conduit formed by the three conduits. Their conduit sections within the chamber would, without the break points, form a syphon conduit formed in one of the possible attitudes where the fuel tank is on its side. A continuous outflow of fuel would commence from the syphon conduit as soon as the fuel column in the outlet conduit becomes lower or fuel emerges from this outlet conduit.
The break point provided in the outlet chamber ensures that when the fuel tank is tilted into the position on its side, a syphon effect normally occurring in the inlet chamber due to fuel flowing out of the outlet conduit is interrupted again in the outlet chamber so that a continuous outflow of fuel is reliably prevented.